Recent advances in genetic analyses have provided a wealth of information regarding specific mutations occurring in particular genes in given disease states. Consequently, use of an individual's genetic information in diagnosis of disease is becoming increasingly prevalent. Genes responsible for disease have been cloned and characterized in a number of cases, and it has been shown that responsible genetic defects may be a gross gene alteration, a small gene alteration, or even in some cases, a point mutation. There are a number of reported examples of diseases caused by genetic mutations. Other uses of DNA analysis, for example in paternity testing, etc., are also important and can be used in accordance with the invention.
Current techniques for genetic analysis have been greatly facilitated by the development and use of polymerase chain reaction (PCR) to amplify selected segments of DNA. The power and sensitivity of the PCR has prompted its application to a wide variety of analytical problems in which detection of DNA or RNA sequences is required.
PCR is capable of amplifying short fragments of DNA, providing short (20 bases or more) nucleotides are supplied as primers. The primers anneal to either end of a span of denatured DNA target and, upon renaturation, enzymes synthesize the intervening complementary sequences by extending the primer along the target strand. During denaturation, the temperature is raised to break apart the target and newly synthesized complementary sequence. Upon cooling, renaturation and annealing, primers bind to the target and the newly made opposite strand and now the primer is extended again creating the complement. The result is that in each cycle of heating and renaturation followed by primer extension, the amount of target sequence is doubled.
One major difficulty with adoption of PCR is the cumbersome nature of the methods of analyzing the reaction's amplified DNA products. Methods for detecting genetic abnormalities and PCR products have been described but they are cumbersome and time consuming. For example, U.S. Pat. No. 5,429,923 issued Jul. 4, 1995 to Seidman, et al., describes a method for detecting mutations in persons having, or suspected of having, hypertrophic cardiomyopathy. That method involves amplifying a DNA sequence suspected of containing the disease associated mutation, combining the amplified product with an RNA probe to produce an RNA-DNA hybrid and detecting the mutation by digesting unhybridized portions of the RNA strand by treating the hybridized product with an RNAse to detect mutations, and then measuring the size of the products of the RNAse reaction to determine whether cleavage of the RNA molecule has occurred.
Other methods used for detecting mutations in DNA sequences, including direct sequencing methods (Maxim and Gilbert, PNAS USA, 74, 560-564, 1977); PCR amplification of specific alleles, PASA (Botttema and Sommer, Muta. Res., 288, 93-102, 1993); and reverse dot blot method (Kawasaki, et al., Methods in Enzymology, 218, 369-81, 1993) have been described. These techniques, while useful, are time consuming and cumbersome and for that reason are not readily adaptable to diagnostic assays for use on a large scale.